The present invention constitutes an improvement over the lift structure disclosed in my prior U.S. Pat. No. 4,568,094 reissued as U.S. Pat. No. Re. 32,736.
A need exists for providing a lift structure that can be used with highway trailers which have the capability of fore and aft trailer wheel adjustment. A difficulty is presented because the lift jack which elevates the trailer bed floor must be attached to move also with the subframe carrying the wheels and not interfere with other operations with the trailer or introduce any problems relating to safety.
Another problem area relates to the adaptation of a highway trailer for transport by rail. The Willetts U.S. Pat. No. 4,385,857 discloses an inter-model rail-highway system for trailer-containers which requires special in-ground facilities at each conversion location.